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Contribution of the School Journey to DailyPhysical Activity in Children Aged 11–12 Years

Elissa F. Southward, MSc, Angie S. Page, PhD, Benedict W. Wheeler, PhD,Ashley R. Cooper, PhD

Background: Active travel is a possible method to increase physical activity in children, but theprecise contribution of walking to school to daily physical activity is unclear.

Purpose: To combine accelerometer and GPS data to quantify moderate-to-vigorous physicalactivity (MVPA) on the walk to and from school in relation to overall daily levels.

Methods: Participants were 141 children aged 11–12 years from the PEACH Project (Personaland Environmental Associated with Children’s Health) in Bristol, England, measured between2008 and 2009. Eighty-four children met the inclusion criteria and were included in the fınalanalysis. Accelerometers measured physical activity, GPS receivers recorded location, and modeof travel was self-reported. Data were analyzed between April and October 2011. Combinedaccelerometer and GPS data were mapped in a GIS. Minutes of MVPAwere compared for schooljourneys taking place between 8:00AM and 9:00AM and between 3:00PM and 5:00PM and in relationto whole-day levels.

Results: Physical activity levels during journeys to and from school were highly similar, andcontributed 22.2 minutes (33.7%) of total daily MVPA. In addition, MVPA on the journey did notdiffer between boys and girls, but because girls have lower levels of daily physical activity than boys,the journey contributed a greater proportion of their daily MVPA (35.6% vs 31.3%).

Conclusions: The journey to and from school is a signifıcant contributor toMVPA in children aged11–12 years. CombiningGPS and accelerometer datawithin aGIS is a useful approach to quantifyingspecifıc journeys.(Am J Prev Med 2012;43(2):201–204) © 2012 American Journal of Preventive Medicine

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Introduction

Increasing physical activity in children is a primaryobjective for public health. Active travel to school is apotential method of increasing physical activity in

hildren.1,2 However, identifying the contribution of theschool journey to physical activity in the context of otheractivities taking place at a similar time presents a meth-odologic challenge, because the temporal pattern, loca-tion, and level of physical activity need to be measured.Combining GPS and accelerometer data is a relativelynew method of assessing the location and level of chil-dren’s physical activity in the environment,3–6 but it has

From the Centre for Exercise, Nutrition and Health Sciences (Southward,Page, Cooper), University of Bristol, Bristol; and the European Centre forEnvironment and Human Health (Wheeler), Peninsula College of Medi-cine and Dentistry, Truro, United Kingdom

Address correspondence to: Elissa F. Southward, MSc, University ofBristol, Centre for Exercise, Nutrition and Health Sciences, School forPolicy Studies, 8 Priory Road, Bristol BS8 1TZ, United Kingdom. E-mail:Elissa.Southward@bristol.ac.uk.

0749-3797/$36.00http://dx.doi.org/10.1016/j.amepre.2012.04.015

© 2012 American Journal of Preventive Medicine • Published by Elsev

been used in only one previous study7 to investigate chil-dren’s active travel to school. This study7 showed thatrimary school children who walked to school recorded.8%of their dailymoderate-to-vigorous physical activityMVPA) during the journey to school but did not inves-igate after-school journeys. The aim of the present studyas to use combined accelerometer and GPS data tonvestigate the contribution that the journey to and fromchool makes to the physical activity of secondary school–ged children.

MethodsParticipants

Data were collected in 2008 and 2009 within the PEACH (Personaland Environmental Associations with Children’sHealth) project, alongitudinal study investigating personal and environmental asso-ciations with children’s physical activity.8 A University of BristolEthics Committee approved the study, and written informed con-sent was obtained from a parent/guardian of all participating chil-

dren. In PEACH, 953 adolescents (aged 11–12 years) were mea-

ier Inc. Am J Prev Med 2012;43(2):201–204 201

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(m

202 Southward et al / Am J Prev Med 2012;43(2):201–204

sured in their fırst year of secondary school, of whom 522 (55%)walked to school. Of these, 141 provided matched accelerometerandGPS data both before and after school, and provide the originalsample for the current study; 84 were included in the fınal analysis.

Measures

Physical activity was measured using accelerometers (ActigraphGT1M) and location was measured using GPS receivers (GarminForetrex 201) worn for 3 school days. Both instruments recordeddata at 10-second epochs. Travelmode to/from school (walk/cycle/

Ordnance Survey Data are © Crown Copyright/database 2011.An Ordnance Survey/EDINA supplied service

0 200 400

Meters

To-sc

From

Roads

GPS points by accelerometer counts per 10 sec

Buildings

n School

≥383 (≥2296 cpm)

<383 (<2296 cpm)

Figure 1. Combined accelerometer and GPS data points com

Note: To-school journeys: 8:00AM–9:00AM; from-school journeys: 3:00PM–5:00PM

ar/bus) was reported in a travel diary. Accelerometer data wererocessed (Kinesoft v3.3.62) to provide values for total dailyVPA (7:00AM to 11:00PM) using the threshold of �2296 counts

per minute.9,10 For weekday periods when the GPS was worn8:00AM–9:00AM and 3:00PM–5:00PM), GPS data were date and timeatched to accelerometer data.9 In both cases, continuous periods

of 60 minutes of zero values, allowing for up to two interruptions,were classifıed as accelerometer nonwear time.11,12 A 2-hourwindow was used for the journey home to account for the varyingfınish times of the secondary schools.

n

n

l journey

hool journey

ing nine pupils’ journeys to and from one secondary school

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-sc

par

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Southward et al / Am J Prev Med 2012;43(2):201–204 203

A

Mapping in GIS

Participants’ home and school locations were mapped in a GIS(ARCGIS 9.3) using postal codes. Individual traces from childrenwho walked to school and provided matched accelerometer andGPS data before and after school were inspected visually in GIS(Figure 1 provides an example of nine children fromone secondaryschool). The journey was defıned as a continual sequence of datapoints allowing for an interruption of up to six epochs (1 minute)and with a clear origin and destination within 200 m of the pupils’home and school. Data points comprising the journeys were seg-mented manually from “nonjourney” data points using the SelectFeatures tool.

Data Analysis

Independent sample t-tests were used to assess differences in phys-ical activity between genders and distance (�3 km and �3 km).Paired sample t-tests were used to test for differences in physicalactivity between the journey to school versus the journey fromschool. Data were analyzed using PASW, version 18.0 (IBM SPSS),between April and October 2011.

ResultsOf the 141 participants who provided some matchedaccelerometer and GPS data before and after school, 84had data from at least one journey both to and fromschool that met the accelerometer/GPS inclusion criteria.Overall, 272 journeys to and fromschoolwere included inanalyses.

Contribution of Journeys to Physical ActivityBased on visual assessment of journeys in GIS, the routetaken from home to school was direct, in all but threeinstances. Similarly, the return journeys followed nearlythe same route home as those taken to school in most(130) instances with onlyminor deviations. There was nodifference in MVPA between the journey to and fromschool (Table 1), with approximately 50% of both jour-neys being MVPA (10.5 of 20.3 minutes and 11.7 of 22.9minutes, respectively) and each journey contributing16%–18% of daily MVPA.There was no difference in physical activity by gender

to and from school. However, all-day MVPA differedbetween boys and girls (p�0.007; Table 1), and thus thejourney contributed a greater proportion to daily MVPA

Table 1. Weekday MVPA levels (M [SD]) of secondary sch

All day (7:00AM–11:00PM)

All Boys Girls

Total (total MVPA[minutes])

65.7 (25.0) 73.2 (31.4) 61.5 (19.5) 14.5

Journey (total MVPA[minutes])

— — — 10.5

VPA, moderate-to-vigorous physical activity

ugust 2012

for girls compared with boys (35.6% vs 31.3%). A linearrelationship was found between distance walked andMVPA (Figure 2). Childrenwith a round trip of�3 km toschool (41%) had higher overall daily MVPA (p�0.001;73.8 minutes vs 60.2 minutes), and the journey contrib-uted a greater proportion to that daily MVPA (39% vs28.6%) than those with shorter journeys.

DiscussionThe present study shows that in this sample of childrenaged 11–12 years, walking to school provides an impor-tant contribution toweekdayMVPA.The contribution ofthe journey to daily MVPA was greater in the presentstudy than in a previous study in primary school childrenfrom London7 (16% vs 3.8%), probably because of thegreater distance traveled by the urban, secondary schoolchildren in the present sample (0.9 miles vs 0.4 miles).Although distance has been identifıed as a barrier toactive travel,13–15 walking longer distances to school canontribute a greater proportion to weekdayMVPA, and ainear association was found between distance walkedndMVPA. Overall, the journey to school appeared to beurposeful and direct in secondary school children, sim-lar to the pattern reported in primary school children.

children

hool (8:00AM–9:00AM) From school (3:00PM–5:00PM)

Boys Girls All Boys Girls

) 13.9 (6.5) 14.8 (8.1) 21.5 (11.5) 23.2 (13.0) 20.7 (10.6)

) 10.0 (5.6) 10.7 (7.6) 11.7 (8.4) 12.9 (8.0) 11.2 (8.6)

0

10

20

30

40

50

60

<1

MV

PA (m

inut

es)

Return journey distance (km)

Means with 95% CI

p for trend = <0.001

1 <2 2 <3 3 <4 4 <5 5 <6

Figure 2. Relationship between distances traveled forjourney to and from school and total-journey MVPAMVPA, moderate-to-vigorous physical activity

ool

To sc

All

(7.6

(6.9

1

1

1

1

1

1

1

1

1

1

2

204 Southward et al / Am J Prev Med 2012;43(2):201–204

Although the activity gained during the journey wasthe same for boys and girls, the contribution walking toschool makes to daily physical activity was greater in girlsas their daily physical activity was lower than boys. Levelsof active travel to school decline through adolescence,16

and these fındings suggest that strategies to maintain orincrease active travel to school may be an important pub-lic health approach to reducing the decline in physicalactivity levels seen throughout adolescence but may beparticularly important for girls, where the decline isgreatest.17–19

To our knowledge, this is the fırst study to use acceler-ometry, GPS, andGIS to quantify physical activity duringthe journey both to and from school. However, there arepotential limitations to using GPS.20 Children were in-structed to switch the GPS receivers off at night in orderto conserve battery life, and some may have failed toswitch the unit on before they left for school or left themswitched on, which would have drained the battery. Inaddition, there is a lag between the GPS connecting withsatellites when a person leaves a building, and the GPSsignal also may be interrupted by buildings or tree cover.These issues resulted in 30% of participants failing toprovide useable journey data and therefore underestima-tion of journey duration.

ConclusionCombining accelerometry, GPS, and GIS can be used toquantify the duration andphysical activity levels of journeysto and from school. The journey to/from school is a majorcontributor to children’sdailyphysical activity levels, partic-ularly for girls, highlighting the importance of supportingactive travel in secondary school–aged children.

This work was supported by the National Prevention ResearchInitiative (G0501311) and World Cancer Research Fund(WCRF UK). The authors acknowledge the Ordnance Surveydata used for analyses here are © Crown copyright/database2011; an Ordnance Survey/EDINA supplied Service.No fınancial disclosures were reported by the authors of this

paper.

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